title: Kinetic and mechanistic investigations of mesotrione degradation in aqueous medium by Fenton process.
abstract: In this work, chemical oxidation of mesotrione herbicide by Fenton process in acidic medium (pH 3.5) was investigated. Total disappearance of mesotrione and up to 95% removal of total organic carbon (TOC) were achieved by Fenton's reagent under optimized initial concentrations of hydrogen peroxide (H(2)O(2)) and ferrous iron (Fe(2+)) at pH 3.5. The time-dependent degradation profiles of mesotrione were satisfactorily fitted by first-order kinetics. Competition kinetic model was used to evaluate a rate constant of 8.8(± 0.2) × 10(9)M(-1) s(-1) for the reaction of mesotrione with hydroxyl radicals. Aromatic and aliphatic intermediates of mesotrione oxidation were identified and quantified by high performance liquid chromatography (HPLC). It seems that the degradation of mesotrione by Fenton process begins with the rupture of mesotrione molecule into two moieties: cyclohexane-1,3-dione derivative and 2-nitro-4-methylsulfonylbenzoic acid. Hydroxylation and release of sulfonyl and/or nitro groups from 2-nitro-4-methylsulfonylbenzoic acid lead to the formation of polyhydroxylated benzoic acid derivatives which undergo an oxidative opening of benzene ring into carboxylic acids that end to be transformed into carbon dioxide.
authors.affiliation: Department of Chemistry, Faculty of Sciences of Gabes, University of Gabes, Cite Erriadh, Zrig 6072, Gabes, Tunisia. nasr.bensalah@issatgb.rnu.tn
authors.forename: Nasr
authors.initials: N
authors.lastname: Bensalah
authors.forename: Ahmed
authors.initials: A
authors.lastname: Khodary
authors.forename: Ahmed
authors.initials: A
authors.lastname: Abdel-Wahab
mesh_terms: D002245:Carbon Dioxide / Q000138:chemical synthesis; D003512:Cyclohexanones / Q000737:chemistry*; D006540:Herbicides / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D003512:Cyclohexanones; C045076:Fenton's reagent; D006540:Herbicides; D014874:Water Pollutants, Chemical; D002245:Carbon Dioxide; C432907:mesotrione; D006861:Hydrogen Peroxide; D007501:Iron